Porous electrode for the electrochemical reaction of organic compounds in two immiscible phases in an electrochemical flow reactor

ABSTRACT

A method for the electrochemical reaction of an organic material, and a device in which a corresponding method is carried out including a porous electrode for the electrochemical reaction of organic compounds in two immiscible phases in an electrochemical flow reactor. A first nonpolar solvent and a first polar electrolyte or a first organic material in the form of a liquid or gas and the first polar electrolyte form a first phase boundary with one another in such a form that the first phase boundary in the electrochemical conversion is at least partly within a first electrode, preferably at an interface between a first lipophilic layer and a second hydrophilic layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2018/097087 filed 28 Dec. 2018, and claims the benefitthereof. The International Application claims the benefit of GermanApplication No. DE 10 2018 201 287.3 filed 29 Jan. 2018. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a method of the electrochemicalconversion of an organic material and to an apparatus in which acorresponding method can be conducted.

BACKGROUND OF INVENTION

The use of electrochemical methods in the synthesis of bulk and finechemicals has always been a major challenge. Many organic substratemolecules are only sparingly soluble in water, but have much bettersolubility in nonpolar solvents, i.e. organic solvents.

However, the use of electrolytes based on organic solvents brings somesignificant disadvantages for electrochemistry.

Firstly, organic solvents and lipophilic organic salts are much moreexpensive than water and inorganic salts.

Secondly, organic electrolytes typically have a significantly poorerconductivity than aqueous electrolytes, which leads to high cellvoltages and high ohmic losses.

Thirdly, the electrolyte in electrochemical processes is often aconsumable material. Even though the overall reaction does not relate towater, it can be consumed locally and then regenerated in the bulkelectrolyte. Every electrochemical process requires a counterpartreaction at the counterelectrode. Many electrochemical conversions,especially organic electrochemical conversions, also include protonsthat have to be generated or consumed by the counterpart reactions. Inthe case of water, this is typically either the reduction or oxidationof water to hydrogen or oxygen. In organic electrolytes, the organicsolvent assumes the role of water, and is broken down at thecounterelectrode. This can be avoided by the use of sacrificial agentsor sacrificial materials, but these in turn massively increase processcosts. At high current density, proton transport by the electrolyte caneven be inadequate for the reaction rate, which can lead to protonationor deprotonation and subsequent breakdown of the electrolyte at theelectrodes.

Therefore, the use of aqueous electrolytes appears very desirable forelectrochemical synthesis. However, the often poor solubility of thereagent molecules in water or even electrolytes having high ionicstrength severely limit substrate supply to the electrodes and hence thecurrent densities.

At present, no general solution to this problem is being employed.Proposals by Beck et al. relate to very thin capillary cells, asdiscussed, for example, in Fritz Beck, Berichte der Bunsen-Gesellschaft1973, 77 (10/11), p. 810-817 and F. Beck, H. Guthke, Chemie-Ing.-Techn.1969, 41 (17), p. 943-950.

US 2013/0228470 A1 discloses a method of converting carbon-based gasesand carbon oxides to longer-chain organic gases.

US 2013/0087451 A1 discloses a membrane-electrode arrangement and anorganic hybrid production apparatus.

The description of U.S. Pat. No. 4,834,847 discloses an electrochemicalcell and a method of the electrolysis of an aqueous solution of analkali metal halide and the preparation of a halogenated hydrocarbon.

There is therefore a need for an effective method of electrochemicalconversion of organic compounds, especially of organic compounds havingzero or sparing solubility in water.

SUMMARY OF INVENTION

The inventors have found that an electrochemical reaction of organiccompounds can effectively be conducted at a phase boundary when this iswithin a multilayer porous electrode comprising a hydrophilic layer anda lipophilic layer.

In a first aspect, the present invention relates to a method ofelectrochemical conversion of a first organic material which is solublein or miscible with a first nonpolar solvent, comprising introducing thefirst organic material into the first nonpolar solvent to produce afirst organic solvent or mixture; providing an electrolysis cellcomprising—a porous first electrode comprising at least one firstlipophilic layer and at least one second hydrophilic layer, where thefirst lipophilic layer and the second hydrophilic layer are porous,and—a second electrode; introducing the first organic solution ormixture into the electrolysis cell in such a way that the first organicsolution or mixture makes contact with the first lipophilic layer of thefirst electrode; introducing a first polar electrolyte into theelectrolysis cell in such a way that the first polar electrolyte makescontact with the second hydrophilic layer of the first electrode and thesecond electrode; and electrochemically converting the first organicmaterial at the first electrode; or providing an electrolysis cellcomprising—a porous first electrode comprising at least one firstlipophilic layer and at least one second hydrophilic layer, where thefirst lipophilic layer and the second hydrophilic layer are porous,and—a second electrode; introducing the first organic material in theform of a liquid or gas into the electrolysis cell in such a way thatthe first organic material makes contact with the first lipophilic layerof the first electrode; introducing a first polar electrolyte into theelectrolysis cell in such a way that the first polar electrolyte makescontact with the second hydrophilic layer of the first electrode and thesecond electrode; and electrochemically converting the first organicmaterial at the first electrode; wherein—the first nonpolar solvent andthe first polar electrolyte or—the first organic material in the form ofa liquid or gas and the first polar electrolyte form a first phaseboundary with one another in such a form that the first phase boundaryin the electrochemical conversion is at least partly within the firstelectrode, preferably at an interface between the first lipophilic layerand the second hydrophilic layer.

In a further aspect, the invention relates to an apparatus forelectrochemical conversion of a first organic material which is solublein or miscible with a first nonpolar solvent, comprising an electrolysiscell, wherein the electrolysis cell comprises—a porous first electrodecomprising at least one first lipophilic layer and at least one secondhydrophilic layer, wherein the first lipophilic layer and the secondhydrophilic layer are porous, and—a second electrode; at least one firstsupply device for the supply of a first solution or mixture of a firstorganic material which is soluble in or miscible with a first nonpolarsolvent in or with a first nonpolar solvent, or for the supply of afirst organic material which is soluble in or miscible with a firstnonpolar solvent, which is set up to supply the first solution ormixture of the first organic material in or with the first nonpolarsolvent, or to supply the first organic material, to the electrolysiscell in such a way that the first organic solution or mixture or thefirst organic material makes contact with the first lipophilic layer ofthe first electrode; and at least one first removal device for theremoval of the remaining first solution or mixture and optionally atleast one first product of the electrochemical conversion of the firstorganic material, or of the remaining first organic material andoptionally at least one first product, or of the remaining firstnonpolar solvent and optionally at least one first product, or of atleast one first product, which is set up to remove the remaining firstsolution or mixture and optionally at least the first product of theelectrochemical conversion of the first organic material, or theremaining first organic material and optionally at least the firstproduct, or the remaining first nonpolar solvent and optionally at leastthe first product, or at least the first product from the electrolysiscell; further comprising at least one second supply device for a firstpolar electrolyte, which is set up to supply the first polar electrolyteto the electrolysis cell in such a way that the first polar electrolytemakes contact with the second hydrophilic layer of the first electrodeand the second electrode, and/or a second removal device for the firstpolar electrolyte and optionally at least one first product of theelectrochemical conversion of the first organic material, which is setup to remove the first polar electrolyte and optionally at least onefirst product of the electrochemical conversion of the first organicmaterial from the electrolysis cell.

Further aspects of the present invention can be inferred from thedependent claims and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings are intended to illustrate embodiments of thepresent invention and impart further understanding thereof. Inassociation with the description, they serve to elucidate concepts andprinciples of the invention. Other embodiments and many of theadvantages mentioned are apparent with regard to the drawings. Theelements of the drawings are not necessarily shown true to scale withone another. Elements, features and components that are the same, havethe same function and the same effect are each given the same referencenumerals in the figures of the drawings, unless stated otherwise.

FIGS. 1 to 6 show, in schematic form, illustrative embodiments of anapparatus of the invention with which the method of the invention can beperformed.

FIGS. 7 and 8 show results that have been achieved in an example of themethod of the invention.

DETAILED DESCRIPTION OF INVENTION

Unless defined differently, technical and scientific expressions usedherein have the same meaning as commonly understood by a person skilledin the art in the technical field of the invention.

Figures given in the context of the present invention relate to % byweight, unless otherwise stated or apparent from the context. In the gasdiffusion electrode of the invention, the percentages by weight add upto 100% by weight.

In the context of the present invention, hydrophobic is understood tomean water-repellent. According to the invention, hydrophobic poresand/or channels are those that repel water. More particularly,hydrophobic properties, according to the invention, are associated withsubstances or molecules having nonpolar groups.

By contrast, hydrophilic is understood to mean the ability to interactwith water and other polar substances.

Lipophilic is understood to mean the property possessed by a substancethat has good solubility in fats and oils or in which fats and oils havegood solubility in turn. More particularly, lipophilic substances areunderstood to mean those that do not mix with and/or dissolve in, and/orrepel, a first polar solvent of the first polar electrolyte, and whichare especially hydrophobic, i.e. water-repellent.

Gas diffusion electrodes (GDE) in general are electrodes in whichliquid, solid and gaseous phases are present, and where a conductivecatalyst in particular catalyzes an electrical reaction between theliquid phase and the gaseous phase.

Different types of design are possible, for example in the form of aporous “all-active material catalyst” optionally with auxiliary layersto adjust the hydrophobicity, in which case, for example, it is possibleto produce a membrane-GDE composite, e.g. AEM-GDE composite; of aconductive porous support to which a catalyst can be applied in a thinlayer, in which case it is likewise again possible to produce amembrane-GDE composite, e.g. AEM-GDE composite; or of a catalyst whichis porous in the composite and may be applied, optionally with additive,directly to a membrane, for example an AEM, and may then form acatalyst-coated membrane (CCM) in the composite.

Standard pressure is 101 325 Pa=1.01325 bar.

Electro-osmosis: Electro-osmosis is understood to mean an electrodynamicphenomenon in which a force in the cathode direction acts on particleshaving a positive zeta potential that are present in solution, and aforce in the anode direction acts on all particles having a negativezeta potential. If a conversion takes place at the electrodes, i.e. ifthere is galvanic current flow, there is also a stream of matter of theparticles having positive zeta potential toward the cathode,irrespective of whether or not the species is involved in theconversion. The same is also true of a negative zeta potential and theanode. If the cathode is porous, the medium is also pumped through theelectrode. This is also referred to as an electro-osmotic pump.

The streams of matter that result from electro-osmosis can also flowcounter to concentration gradients. Diffusion-related currents thatcompensate for the concentration gradients can be overcompensated as aresult.

A separator is a two-dimensional structure designed to separateelectrodes and/or electrolytes or the reaction spaces or half-cells inan electrolysis cell from one another. It is electrically insulating inrespect of the electrodes of an electrolysis cell itself and can,especially in particular embodiments, at least partly prevent,preferably essentially prevent, the mixing of two electrolytes and/or,if appropriate, of product gases and/or reaction gases of anelectrochemical reaction in half-cells separated by the separator. Moreparticularly, a separator can prevent the mixing of product gases and/orreaction gases of half-cells separated thereby. However, a separatorpermits adequate exchange of mass and in particular of charge carrierswith an electrolyte medium, in order to enable ionic flow. Asseparators, for example, frits, membranes, diaphragms etc. generallyallow diffusive mass transfer of liquids and dissolved substances.

A diaphragm is a specific separator which is designed to electricallyinsulate electrodes from one another but does not have any intrinsic ionconductivity or marked transport selectivity. More particularly, adiaphragm, in particular embodiments, can also prevent the mixing ofreaction gases in electrolyte streams. It is a two-dimensionalcomponent, for example a paper-like or porous composite material. Ionconductivity is achieved in a diaphragm via the absorptivity of thediaphragm toward the electrolyte. Diaphragms therefore frequently have avery sharp pore size distribution.

A membrane is an electrically insulating polymer film designed toelectrically insulate electrodes from one another and preferably toessentially prevent the mixing of two electrolytes and gas bubblespresent therein, especially to prevent the mixing of gas bubbles atleast present therein. However, the membrane may have an active iontransport function by virtue of appropriate chemical groups. If this iontransport is ion-selective for one or more ions, for example cationsand/or protons or anions, reference is also made to an ion-selectivemembrane. An ion-selective membrane is correspondingly an electricallyinsulating polymer film for the electrodes of the electrolysis cell,which is designed to electrically insulate electrodes from one anotherand especially to essentially prevent the mixing of two electrolytes andgas bubbles present therein, especially to prevent the mixing of gasbubbles at least present therein. The polymer in such an ion-selectivemembrane bears charged functional groups with mobile counterions andtherefore constitutes a macromolecular salt, an acid and/or a base.Swollen in a pure solvent, for example water, these membranes haveintrinsic ion conductivity. In electrolyte solutions, they generallyalso have selectivity with respect to the nature of the charge carriertransported. The ionic functionalization under potential can also leadto formation of new charge carriers in the membrane that are thenresponsible for ion transport in the membrane.

In a first aspect, the present invention relates to a method ofelectrochemical conversion of a first organic material which is solublein or miscible with a first nonpolar solvent, comprising introducing thefirst organic material into the first nonpolar solvent to produce afirst organic solvent or mixture; providing an electrolysis cellcomprising—a porous first electrode comprising at least one firstlipophilic layer and at least one second hydrophilic layer, where thefirst lipophilic layer and the second hydrophilic layer are porous,and—a second electrode; introducing the first organic solution ormixture into the electrolysis cell in such a way that the first organicsolution or mixture makes contact with the first lipophilic layer of thefirst electrode; introducing a first polar electrolyte into theelectrolysis cell in such a way that the first polar electrolyte makescontact with the second hydrophilic layer of the first electrode and thesecond electrode; and electrochemically converting the first organicmaterial at the first electrode; or providing an electrolysis cellcomprising—a porous first electrode comprising at least one firstlipophilic layer and at least one second hydrophilic layer, where thefirst lipophilic layer and the second hydrophilic layer are porous,and—a second electrode; introducing the first organic material in theform of a liquid or gas into the electrolysis cell in such a way thatthe first organic material makes contact with the first lipophilic layerof the first electrode; introducing a first polar electrolyte into theelectrolysis cell in such a way that the first polar electrolyte makescontact with the second hydrophilic layer of the first electrode and thesecond electrode; and electrochemically converting the first organicmaterial at the first electrode; wherein—the first nonpolar solvent andthe first polar electrolyte or—the first organic material in the form ofa liquid or gas and the first polar electrolyte form a first phaseboundary with one another in such a form that the first phase boundaryin the electrochemical conversion is at least partly within the firstelectrode, preferably at an interface between the first lipophilic layerand the second hydrophilic layer.

In the method of the invention, the first organic material is notparticularly restricted, provided that it is soluble in or miscible witha first nonpolar solvent. In this case, as is clear in the secondembodiment of the method of the invention, it is not even necessary forthe first nonpolar solvent to be employed in the method if the firstorganic material is liquid or gaseous. It is important merely that aphase boundary forms within the first electrode. For this purpose, it isconsequently also sufficient for the first organic material and thefirst polar electrolyte to form a phase boundary, i.e. two separatephases. For this purpose, it is sufficient, for example, when the firstorganic material, in particular embodiments, is nonpolar.

In the first embodiment of the present method, this phase boundary isformed between the first solution or mixture in which the nonpolarsolvent has been mixed with or has dissolved the first organic material,and the first polar electrolyte. In this respect, it is pointed outthat, in this first embodiment of the method of the invention, the firstorganic material may take the form of a solid, liquid or gas that canthen be dissolved in or mixed with the first nonpolar solvent. The firstorganic material here need not necessarily be nonpolar if it dissolvesin or mixes with the first nonpolar solvent.

The first organic material can be introduced here in the form of aliquid or gas, especially liquid, into a nonpolar solvent, for examplein order to adjust the viscosity of the first organic material, in orderthat it can achieve better ingress to and can preferably penetrate intothe first electrode, it being simpler to reach the triphasic interfacein the first electrode especially in the case that the first electrodetakes the form of a gas diffusion electrode. Moreover, it is more easilypossible through the mixing with the first nonpolar solvent or thedissolving in the first nonpolar solvent to adjust the concentration ofthe first organic material through the dilution, by means of which thereaction at the electrode can be better controlled, and overreductioncan especially be reduced or avoided.

In the method of the invention, there are thus two variants forelectrochemical conversion of the first organic material, depending onwhether or not it is in the form of a fluid, i.e. liquid or gas. If thefirst organic material is in the form of a fluid, it can also beintroduced directly as such into the electrolysis cell since it can forma first phase boundary with the first polar electrolyte. If the firstorganic material is in solid form, it must be dissolved in a firstnonpolar solvent for it to be able to be introduced into theelectrolysis cell and for the first nonpolar solvent to form the firstphase boundary with the first polar electrolyte therein. In addition, itis of course also possible for the first organic material in the form ofa fluid to be mixed with or dissolved in a first nonpolar solvent, forexample in order to be able to form a better first phase boundary withthe first polar electrolyte.

Apart from that, there is no further restriction in the first organicmaterial that is soluble in or miscible with a first nonpolar solvent.

Nor is there any particular restriction in the first organic materialwith regard to possible classes of compounds. It may be a saturated,unsaturated and/or aromatic hydrocarbon which is substituted orunsubstituted, where the substituents are not particularly restricted,provided that the first organic material is soluble in or miscible witha first nonpolar solvent. For example, it is also possible to use polarsubstituents when the first organic material itself is still soluble inor miscible with a first nonpolar solvent. For that reason, the natureof the substituents is not particularly restricted either, nor is thenumber of carbons in the first organic material. In particularembodiments, the first organic material is aromatic or at leastcomprises an aromatic moiety in the structure. For example, the firstorganic material for a reduction may be selected from unsaturatedhydrocarbons, aldehydes, ketones, nitro compounds, nitroso compounds,nitriles, etc.; and for an oxidation may be selected from alcohols,unsaturated hydrocarbons, amines, mercaptans, etc.

In particular embodiments, the first organic material is especiallyimmiscible with water and/or insoluble in water as solvent in the firstpolar electrolyte. In particular embodiments, the first organic materialis hydrophobic, especially when it is in the form of a liquid or gas.

The first nonpolar solvent is likewise not particularly restricted,provided that it forms a phase boundary with the first polarelectrolyte. This may be a pure compound, for example optionallysubstituted alkanes such as pentane, hexane, heptane, octane, etc.,partly or fully halogenated alkanes such as dichloromethane, etc.;substituted or unsubstituted aromatics such as benzene, toluene, etc.;alkenes; alkynes; esters; ethers such as diethyl ether, tetrahydrofuran,etc. It is also possible to use mixtures of nonpolar solvents. The firstnonpolar solvent is especially not soluble with water or in water assolvent in the first polar electrolyte, i.e. in particular hydrophobic.

The first nonpolar solvent need not be electrically conductive, but itis not impossible that conductive nonpolar solvents such as ionicliquids (ILs) are used, provided that they are stable and immisciblewith the first polar electrolyte, especially an aqueous phase. Sincehydrophobic organic salt melts in particular, for example Bu₃MeP⁺((CF₃)SO₂)N⁻, as ionic liquids often have very desirable dissolutionproperties, they can also be used in place of the first nonpolarsolvent. The hydrophobic ionic liquids here are not particularlyrestricted.

A first nonpolar solvent is employed, for example, in the embodimentsset out above for the first organic compound. In addition, a nonpolarsolvent may also be required if a first organic product which is solidat the reaction temperature of the electrochemical conversion is formedat the porous first electrode in the electrochemical reaction, does notdissolve in the first polar electrolyte and is accordingly to be removedagain from the first electrode with the first polar solvent.

What is meant here by the expression “miscible with a first nonpolarsolvent” is that the mixing with nonpolar solvent does not form twophases, i.e. a phase boundary.

The introducing of the first material into the first nonpolar solventfor preparation of a first organic solution or mixture is notparticularly restricted. For example, it can be mixed, added dropwise,stirred, etc. However, preference is given to preparing a homogeneoussolution in the introducing of the first organic material into the firstnonpolar solvent.

The first polar electrolyte is likewise not particularly restricted. Inparticular embodiments, the first polar electrolyte is liquid. Inparticular embodiments, the first polar electrolyte is protic. Inparticular embodiments, the first polar electrolyte especially comprisesat least one first polar solvent such as, for example, water; alcoholssuch as methanol, ethanol, propanol, butanol, phenol, etc.; carboxylicacids such as formic acid, acetic acid, propionic acid, etc.; aldehydessuch as acetaldehyde, etc., ketones such as acetone; acids such asH₂SO₄, HCl, HBr, etc.; sulfones; amines; nitriles; amides; lactones;sulfoxides; etc., and mixtures; and especially water as polar solvent.In addition, it comprises compounds such as conductive salts that aresoluble in the at least one first polar solvent and enable ioniccontacting of the electrodes, i.e. of the first and second electrodes ofthe electrolysis cell, such that charge carrier transport, for exampleion transport, can take place. The conductive salt is not particularlyrestricted, and comprises, for example, salts of alkali metals and/oralkaline earth metals, for example of lithium, sodium, potassium,magnesium, calcium, etc., for example halides, sulfates, etc. Inaddition, the first polar electrolyte may also contain substancestypically present in electrolytes, for example pH regulators, buffers,etc.

As well as the first polar solvents mentioned, it is also possible touse other, especially protic, solvents in the first polar electrolyte,either alone as solvent or in combination with the abovementioned polarsolvents. At low temperatures of <15° C., it is also possible to use HF,for example. It is also equally possible here to use salt melts or ionicliquids such as ethylmethylimidazolium hydrogensulfate and/ortriethanolmethylammonium methylsulfate, provided that they are polar.More particularly, it is possible to use those further, preferablyprotic, solvents in reactions in the electrolysis cell that neitherconsume nor produce water—for example with regard to the secondelectrode, provided that the reaction takes place within their stabilitywindow. The polar solvent can be suitably chosen accordingly.

In particular embodiments, the first polar electrolyte contains waterand optionally at least one salt, for example one of those specifiedabove. In particular embodiments, the first polar electrolyte—alsoreferred to hereinafter as first phase if appropriate—is an aqueoussolution of salts that can serve as electrolyte and optionallyconsumable materials, i.e. can accordingly, if appropriate, be suppliedto the electrolysis cell via a feed device and removed from theelectrolysis cell via a removal device.

By contrast, the first organic solution or mixture, or the first organicmaterial in the form of a liquid or gas, forms a second phase which is anonpolar phase that contains the first organic material as substrate.This nonpolar phase has only limited or zero miscibility with the polarelectrolyte as the first phase, for example the aqueous electrolyte,such that a phase boundary forms. As already set out above, the firstorganic material as substrate must be soluble in or miscible with anonpolar solvent, but may be solid, liquid or gaseous. It is alsopossible for the first organic material to be the nonpolar phase in theform of a pure substrate. The nonpolar phase need not be electricallyconductive. In particular embodiments in the first variant, thesubstrate is a substrate solution in a nonpolar organic solvent.

The providing of an electrolysis cell comprising a porous firstelectrode comprising at least one first lipophilic layer and at leastone second hydrophilic layer, wherein the first lipophilic layer and thesecond hydrophilic layer are porous, and a second electrode is likewisenot particularly restricted. Apart from the two electrodes, wherein thesecond electrode is not particularly restricted, the electrolysis cellis likewise not particularly restricted in terms of its material and itsconfiguration. Illustrative configurations of the electrolysis cell aredescribed hereinafter.

The first electrode is porous, i.e. has pores, and comprises at leastone first lipophilic layer and at least one second hydrophilic layer.However, it is not impossible that the first electrode also comprisesregions that do not have a porous configuration, for example a grid forelectrical contact connection, in which case, however, a layer mayoptionally be pressed into the grid in order to form a porous structurein turn. The first lipophilic layer is porous. The second hydrophiliclayer is porous. More particularly, the first lipophilic layer and thesecond hydrophilic layer are in contact with one another. If the twolayers are in contact and the two layers are porous, it is possible toreduce or prevent the formation of by-products that have to be removed,for example of OH⁻ in the case of use of water in the polar electrolyte.

The pore size here is not particularly restricted, but in particularembodiments is in the range from 0.1 to 500 μm, for example in the rangefrom 0.2 to 100 μm, e.g. 0.5 to 10 μm. Pore size can be suitablydetermined, for example, by means of porosimetry. The first electrodethus has at least one region with pores, especially with pores presentin the region in which the electrochemical conversion of the firstorganic material is effected, i.e. especially in the region in which thefirst lipophilic layer and the second hydrophilic layer adjoin oneanother. In this region, in particular embodiments, there is alsoaccordingly at least one first electrocatalyst or catalyst for theelectrochemical conversion of the first organic material which is notparticularly restricted. The first electrocatalyst may comprise, forexample, metals and/or compounds thereof, for example Cu, Ag, Au, Pd,Zr, Zn, Cd, Pb, Ir, Sn, Zn, Pb, Ti, Fe, Ni, Co, Rh, Ru, W, Mo, andcompounds thereof, for example oxides or suitable polymorphs of carbonetc., and mixtures and or alloys thereof, and may be suitably adapted toa desired electrochemical conversion. For example, it may also beintroduced into the second hydrophilic layer. Preferably, however, thefirst electrocatalyst is not present in the first lipophilic layer.

However, the first electrode may as a whole also consist only ofmaterials comprising pores, i.e. in particular embodiments comprisessolely porous layers. With porous layers, good separation of the twophases in the process in particular is possible, i.e. of the nonpolarphase of the nonpolar solution or mixture or of the nonpolar solvent,and of the polar phase of the polar electrolyte. In this way too, it ispossible to increase the area-based current density within theelectrode, especially when the first lipophilic layer and/or the secondhydrophilic layer are conductive. Moreover, the electrochemicallycatalyzed reaction to give the desired product is improved by the porestructure. In particular embodiments, the first electrode consists ofthe first lipophilic layer and the second hydrophilic layer, andoptionally a material for electrical contact connection. It isoptionally possible for the first electrode in such embodiments also tobe coated, for example on the lipophilic layer on the side which is incontact with the first nonpolar solution or mixture, or the firstorganic solvent in the form of a liquid or gas, as bulk, and/or on thehydrophilic layer on the side which is in contact with the first polarelectrolyte as bulk.

Within the present concept, i.e. in relation to the present process andalso the present apparatus, the first electrode forms a “three-phasehalf-cell” within the electrolysis cell. Within the concept, at leastone electrochemical half-cell thus comprises three phases, namely thesolid but porous electrode that lies between two immiscible fluidphases, one of which is nonpolar and contains the substrate, and theother is a polar electrolyte that carries the ion current and canoptionally serve as consumable material. The electrolyte phase here isthat directed toward the counterelectrode.

The porous first electrode has amphiphilic character and comprises atleast two layers, one of which is more hydrophilic and the other morelipophilic. Both layers here are preferably electrically conductive andporous. Since electrodes, owing to electrochemical stress, generallybecome more hydrophilic, it is also possible to introduce the electricalcontact or electrical contact connection into the hydrophilic layer orinto the layer boundary.

The first lipophilic layer is not particularly restricted provided thatit is lipophilic. In particular embodiments, it is hydrophobic. Thefirst lipophilic layer is porous, i.e. has pores. As a result, thetransport of the first organic material, optionally dissolved in ormixed with the first nonpolar solvent, can be controlled, such that, ifappropriate, no excess reaction takes place. The first lipophilic layermay also be constructed, for example, as a grid or the like, althoughthis is not preferred.

In particular embodiments, the first lipophilic layer is electricallyconductive. In particular embodiments, the first lipophilic layer iselectrochemically inactive as catalyst, especially when it is introducedinto the first polar electrolyte, for example an aqueous electrolyte. Inthis way, it is especially possible to ensure that no electrochemicalreactions take place when a portion of this layer comes into contactwith the electrolyte. Otherwise, the electroosmotic pressure in theporous electrode can draw the electrolyte into the lipophilic layer andforce the liquid-liquid interface out of the first electrode, such thatthe substrate supply thereof can be cut off as a result.

The construction of the first lipophilic layer is not particularlyrestricted, and it may be constructed in a meshlike manner, as a scrim,loop-drawn knit or loop-formed knit, in a spongelike manner, etc. Inparticular embodiments, the first lipophilic layer is realized bybinding particles that are especially inert, conductive and/orhydrophobic, e.g. hydrophobic carbon and/or glassy carbon, with ahydrophobic binder material such as PTFE (polytetrafluoroethylene),PCTFE (polychlorotrifluoroethylene), PFA (perfluoroalkoxy) and/or FEP(fluoroethylene-propylene). The production of the first lipophilic layermay be simultaneous with the production of the second hydrophilic layerand optionally further layers, for example by means of joint rolling,coextrusion, etc., or separately therefrom, in which case the layers cansubsequently be suitably bonded.

In particular embodiments, the first lipophilic layer has essentiallyzero catalytic activity in respect of the first polar electrolyte, i.e.has a high overvoltage for the competing reaction with the first polarelectrolyte, for example a high overvoltage for the evolution ofhydrogen or evolution of oxygen, according to how the electrode isconnected. In particular embodiments, the first lipophilic layercomprises hydrophobic, preferably conductive, first particles and/or atleast one first hydrophobic binder. If the first lipophilic layer of thefirst electrode is in contact with a gas as first organic material, thefirst electrode may also take the form of a gas diffusion electrode, andso the first lipophilic layer may be designed accordingly.

The second hydrophilic layer is not particularly restricted either andis especially wettable with the first polar electrolyte, especiallywater. In particular embodiments, the second hydrophilic layer comprisesa first electrocatalyst and optionally at least one second binder. Inparticular embodiments, the hydrophilic layer is thus theelectrochemically active layer. It contains or even consists essentiallyof the first electrocatalyst. It is preferably also hydrophilic, porousand/or electrically conductive.

In principle, the second hydrophilic layer may also be realized withbound particles, optionally with at least one binder. By contrast,however, these particles are at least partially electrochemically activecatalyst particles. This layer preferably consists of the firstelectrocatalyst in a large portion. However, embedding of the firstelectrocatalyst into an inert conductive matrix is also possible. Thebinder used may also, for example, be PTFE or PTFCE. In order to furtherincrease the hydrophilic character of this layer, these polymers may,however, also be partly replaced by hydrophilic binder polymers such aspolyarylsulfones, e.g. PPSU (polyphenylene-sulfone).

It is also possible to introduce hydrophilic additives, e.g. metaloxides, for example Al₂O₃, TiO₂, ZnO, Y₂O₃, etc., into the secondhydrophilic layer. In particular embodiments, the second hydrophiliclayer thus comprises first hydrophilic additives, especially metaloxides.

In particular embodiments, the second hydrophilic layer may alsocomprise an inherently ion-conductive additive such as a cation or anionexchanger. To achieve inherent ion conductivity, it is thus possible tointroduce ion conductivity additives such as ion exchange resins orother solid electrolytes into this layer, which are not particularlyrestricted. In particular embodiments, the second hydrophilic layercomprises a first ion-conducting additive, especially a cation or anionexchanger.

As well as the first lipophilic layer and the second hydrophilic layer,the first electrode may also comprise further “layers”.

For better current distribution in large electrodes, it is possible, forexample, to add a first current collector which is not particularlyrestricted in terms of material and form and may comprise, for example,a metal, a conductive oxide, a ceramic, a conductive polymer, etc.,which may take the form, for example, of a lattice, braid, loop-formedknit, loop-drawn knit or the like. Since the first current collectorshould not come into contact with the first polar electrolyte,especially an aqueous electrolyte, it is preferably connected to thefirst lipophilic layer. In particular embodiments, the first electrodethus comprises a first current collector which is preferably not incontact with the second hydrophilic layer. It is also possible for afirst current collector to be realized, for example, as an incompletemetal coating, for example, of the first lipophilic layer. Preference isgiven to using a metal braid since it can also offer additionalmechanical support. The first current collector, for example, may lie onor be embedded in the first lipophilic layer, for example in that it isrolled with said layer.

As well as the first lipophilic layer and the second hydrophilic layerand optionally the first current collector, the first electrode may alsocomprise further additional layers. For example, a protective layer maybe provided as a “top layer” on the second hydrophilic layer, forexample in the form of a hydrophilic membrane for the second hydrophiliclayer for protection of the layer. The hydrophilic membrane mayoptionally be soaked and passed through by the electrolyte. The mainfunction of this layer is the protection of the electrode from erosion.This layer may also form an additional flow barrier in order to preventmigration of the liquid-liquid boundary. In particular embodiments, sucha membrane on the second hydrophilic layer is porous.

It is also or alternatively possible to provide, for example, aprotective layer as “backing layer” on the first lipophilic, e.g.hydrophobic, layer, for example in the form of a hydrophobic membranefor the first lipophilic layer, for example for better wetting with thenonpolar phases, for example based on polyamide, etc., in order toprevent erosions and/or avoid flows through the electrode. Since thisside, however, is on the opposite side from the counterelectrode,however, it is preferably used for electrical contact connection, whichcorrespondingly means that such a hydrophobic membrane is not verypracticable. In such a case, the layer should thus then preferably notbe continuous, and, for example, wires of the current collector, ifpresent, may protrude therefrom.

The second hydrophilic layer may also be fused to an ion-conductivemembrane. In particular, inherent ion conductivity of the secondhydrophilic layer is preferable here, said layer especiallycorresponding to the ion-conductive membrane. Like the top layerdiscussed above, this layer also offers erosion protection and flowresistance. However, it may additionally be used to increase the totalcharge transport between the first electrode and the first polarelectrolyte. For example, anion exchange membranes may be used in orderto limit charge transport in cathodes to anions that leave the firstelectrode in the polar electrolytes and to protons that penetrate viathe Grotthuss mechanism. In a corresponding manner, it is possible touse cation exchange membranes, for example, at the anode. This can beused to control the electroosmotic pressure and/or to protect theelectrode from electrolyte cations and/or anions. Just like cathodes, itis thus also possible to shield anodes from electrolyte anions Like thetop layer and the backing layer, the anion and/or cation exchangemembranes are also not particularly restricted. The anion and/or cationexchange membranes may be realized, for example, as anion exchangemembrane (AEM), cation exchange membrane (CEM), or bipolar membrane ineither direction.

In addition, in the first electrode, at least one support constructionmay be incorporated as mechanical support, for example in the form ofinsulation polymer mats, etc., for example including into each layer ofthe electrode.

In the electrolysis cell, the first electrode may be connected ascathode or anode, according to the desired electrochemical conversion,i.e. reduction or oxidation.

In addition, the electrolysis cell comprises a second electrode which isnot particularly restricted. In terms of its construction, it may besimilar to or different than that of the first electrode, according tothe desired half-cell reaction. For instance, the second electrode maytake the form of an all-active electrode or solid electrode, of a gasdiffusion electrode, of a porous bound catalyst structure, of aparticulate catalyst on a support, of a coating of a particulatecatalyst on a membrane, of a porous conductive support into which acatalyst has been impregnated, and/or of a noncontinuous sheetlikestructure. Water can also be electrolyzed to H₂ or O₂ at the secondelectrode, for example in the case of an aqueous first polarelectrolyte.

The second electrode may also be executed as a direct catalyst coatingon a membrane or in direct contact with a membrane, especially if it isa noncontinuous planar construction such as mesh, for example. Thesecond electrode may also be insulated by a separator in order toprotect the first electrode from gases that form at the secondelectrode.

In the above cases, in particular embodiments, a first organic materialis converted at the first electrode, while there is preferably aconversion of the first polar electrolyte or a constituent thereof, forexample water, at the second electrode.

The arrangement of the electrodes is not particularly restricted. Forexample, they may be arranged essentially in parallel, such that it iscorrespondingly possible to form electrode stacks, or else they may bein a concentric arrangement, etc.

In particular embodiments, the second electrode comprises at least onethird lipophilic layer and at least one fourth hydrophilic layer,wherein the third lipophilic layer and the fourth hydrophilic layer arepreferably porous, wherein the first polar electrolyte makes contactwith the fourth hydrophilic layer of the second electrode, furthercomprising introducing—a second organic material in the form of a liquidor gas, or—a second organic solution or mixture comprising a secondorganic material which is soluble in or miscible with a second nonpolarsolvent, and a second nonpolar solvent, into the electrolysis cell insuch a way that the first organic material or the second organicsolution or mixture makes contact with the third lipophilic layer of thesecond electrode, wherein the second organic material iselectrochemically converted at the second electrode. In this case, forexample, two organic substrates may be converted simultaneously in themanner of a tandem electrolysis.

In such embodiments, the second electrode is similar to the firstelectrode or relatively large parts or the entirety thereof may evencorrespond thereto. If, for example, the first electrode is the cathode,the second electrode could be constructed, in a mirror image, as theanode in the layer structure toward the middle of the electrolysis cell(between the two electrodes).

In such a second electrode, the third lipophilic layer may be formedfrom the same material as the first lipophilic layer, or from anothermaterial mentioned for the first lipophilic layer. It is likewisepossible for the fourth hydrophilic layer to be constructed from thesame material as the second lipophilic layer, or from another material.More particularly, the fourth hydrophilic layer may include the sameelectrocatalyst as the second hydrophilic layer as the secondelectrocatalyst, or a different one, but preferably one selected fromthe materials mentioned above for the first electrocatalyst. Any desiredcombinations are possible here, including with regard to the presence offurther layers in the second electrode, for instance a second currentcollector may correspond to the first current collector or else may bedifferent therefrom, but may be made of one of the materials mentionedfor the first current collector. With regard to the form as well, theindividual layers may be the same or different. Preferably, however, thethird lipophilic layer and/or the fourth hydrophilic layer are porous.Preferably, the third lipophilic layer and the fourth hydrophilic layerare in contact with one another. It is also possible, in a mannercorresponding to the first electrode, for membranes to be applied to thelayers of the second electrode in such embodiments, for example ahydrophobic membrane on the third lipophilic layer and/or a hydrophilicmembrane or ion exchange membrane on the fourth hydrophilic layer. Heretoo, the materials usable may correspond to those in the abovementionedcorresponding analogous layers, wherein the layers may be the same ordifferent. It is also possible for at least one support construction tobe provided in the second electrode, for example including for alllayers.

In addition, the second organic material may correspond to the firstorganic material or may be different therefrom. Since, however,different reactions can proceed at the anode than at the cathode, thefirst organic material and the second organic material are different,for example including with regard to the aggregate form and with regardto whether or not they are in a solution or mixture. Correspondingly, itis also possible for the second nonpolar solvent, if it is used in theprocess, to correspond to the first nonpolar solvent, if it is used, orbe different therefrom.

In the embodiments with the second electrode comprising the fourthhydrophilic layer, this is typically in contact with the first polarelectrolyte. However, it is also conceivable that the electrolysis cellcomprises at least one separator, for example a diaphragm and/or amembrane—which are not particularly restricted—between the firstelectrode and the second electrode, such that the space between the twoelectrodes is divided into two component spaces, in which case it ispossible for a first polar electrolyte to be introduced into onecomponent space—for example adjoining the second hydrophilic layer ofthe first electrode—and for a second polar electrolyte that maycorrespond to the first polar electrolyte or be different therefrom tobe introduced into another component space—for example adjoining thefourth hydrophilic layer of the second electrode or generally the secondelectrode, although the materials for this second two polar electrolytemay be the same as mentioned for the first polar electrolyte. However,this is not preferred. In particular embodiments, the second hydrophiliclayer of the first electrode makes at least partial contact with a firstseparator.

Alternatively or additionally, it is also optionally possible to usefurther separators and optionally further polar electrolytes with whichproduct extraction from the first polar electrolyte is possible, forexample when the electrochemical conversion generates an organic productsoluble in the first polar electrolyte at the first and optionallysecond electrodes. In that case, it is easily possible here to purifythe organic product.

In particular embodiments, the second hydrophilic layer of the firstelectrode and the fourth hydrophilic layer of the second electrode makeat least partial contact with a first separator on opposite sides of thefirst separator. In such embodiments, the first polar electrolyte is atleast partly present in the first separator. In particular embodiments,the first separator has been swollen by the first polar electrolyte. Inthis way, it is possible to enable good contact between the twoelectrodes with a small electrolyte volume. This is advantageousespecially when the first polar electrolyte is not converted, i.e. notconsumed, or can easily be replenished.

As well as separators, the electrolysis cell may also comprise furtherconstituents that are typically used for electrolysis cells, such ascorresponding feed and drain devices for the first polar electrolyte,the first nonpolar solution or mixture or the first organic material inthe form of a liquid or gas, and optionally for the second nonpolarsolution or mixture or the second organic material in the form of aliquid or gas, heating and/or cooling devices, pumps, valves, housing,etc. However, the electrolysis cell comprises at least one power source.

In the method of the invention, the introducing of the first organicsolution or mixture, or of the first organic material in the form of aliquid or gas, into the electrolysis cell in such a way that the firstorganic solution or mixture or the first organic material makes contactwith the first lipophilic layer of the first electrode, the introducingof a first polar electrolyte into the electrolysis cell in such a waythat the first polar electrolyte makes contact with the secondhydrophilic layer of the first electrode and the second electrode, andany introducing of the second organic solution or mixture comprising asecond organic material or the second organic material in the form of aliquid or gas in such a way that the second organic solution or mixtureor the second organic material makes contact with the third lipophiliclayer of the second electrode are not particularly restricted, and theintroduction can be effected simultaneously or at different times.

After the introducing of the first organic solution or mixture, or ofthe first organic material in the form of a liquid or gas, as nonpolarphase, and after the introducing of the first polar electrolyte as polarphase, the nonpolar phase and polar phase form a first phase boundary insuch a form that the first phase boundary in the electrochemicalconversion is at least partly within the first electrode, preferably atan interface between the first lipophilic layer and the secondhydrophilic layer. The use of the first hydrophilic layer and of thefirst lipophilic layer can ensure here that the first phase boundaryforms at least partly and preferably completely in the first electrodein the electrochemical conversion, such that the first organic materialcan arrive there for electrochemical conversion, but it issimultaneously also possible to establish a suitable cell voltage bymeans of the first polar electrolyte. The first phase boundary asliquid-liquid phase boundary must thus be at least partly in contactwith the electrode surface. In this way, it is also possible to form atriphasic interface at which an electrocatalyst of the first electrode,for example the first catalyst, simultaneously has access to electricalcontact, ion contact, optionally protons from the first polarelectrolyte, and the first organic material as substrate. In order toachieve high current densities, the total area of these three phaseinterfaces should be at a maximum. For this purpose, it is possible toposition the liquid-liquid interface within a porous electrode.

In order that the liquid-liquid boundary remains at or within theelectrode, it is necessary for the electrode to have an amphiphiliccharacter, as achieved by virtue of the lipophilic layer and thehydrophilic layer, with the side toward the counterelectrode beingwettable by the polar, for example aqueous, phase, while the other sideis wettable by the nonpolar phase. The electrode thus has at least twolayers. In order, however, to bring the phases into contact, the secondhydrophilic layer preferably also includes a certain amount oflipophilic pores, for example ≤30%, preferably ≤25%, further preferably≤20%, based on the pores of the hydrophilic layer.

Corresponding considerations relate to the second electrode if it hasthe third lipophilic layer and the fourth hydrophilic layer and a secondphase boundary forms between the first polar electrolyte (or another,for example second, polar electrolyte) and the second nonpolar solutionor mixture or the second organic material in the form of a liquid orgas.

The electrochemical conversion of the first organic material or of thefirst organic material in the form of a liquid or gas at the firstelectrode, and if appropriate the electrochemical conversion of thesecond organic material, or of the second organic material in the formof a liquid or gas, are not particularly restricted and may be suitablyadapted to a reactant and a desired product.

The electrochemical conversion of the first organic material gives riseto at least one first organic product which, according to its solubilityand polarity, can be removed from the first electrode via the firstnonpolar phase, i.e. first nonpolar solution or mixture or first organicmaterial, or the first polar electrolyte as polar phase. It can eitherbe discharged from the electrolysis cell via the corresponding phase andthen optionally removed/extracted outside and optionally purified, orextracted into further phases in the electrolysis cell, for example bymeans of suitable separators, and hence optionally separated fromby-products.

It should be noted here that, as well as the electrochemical conversionat the first electrode—in which at least one first organic product isformed—an electrochemical conversion also takes place at the secondelectrode, in which at least one second inorganic product, for examplechlorine, oxygen, etc., or at least one second organic product may form,for example with the second electrode comprising the third lipophiliclayer and the fourth hydrophilic layer. It is of course possible in thatcase, in the method of the invention, for the first organic product tobe reacted further with the second inorganic or organic product,preferably after previous removal and purification thereof, such that itis possible by the method of the invention not just to perform anorganic synthesis step by electrochemical means, but simultaneously alsoto obtain a further reactant for a subsequent step, in which case it isalso possible, for example, to use waste heat from the electrochemicalconversion for this further conversion in the subsequent step.

As set out above, the method of the invention may also be followed by anextraction. In some cases, for example the cathodic reduction of nitrocompounds or the anodic oxidation of aldehydes, hydrophilicity of theproduct is increased, which leads to partial extraction into theelectrolyte. In this case, the electrolyte, after leaving the cell, inparticular embodiments, will go through an extraction vessel with pureorganic solvent to recover the product.

For these applications, the electrolyte gap can also be provided with anunlimited number of separators, e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10 or moreseparators, as also set out above, to simplify the extraction.

A further aspect of the present invention is directed to an apparatusfor electrochemical conversion of a first organic material which issoluble in or miscible with a first nonpolar solvent, comprising anelectrolysis cell, wherein the electrolysis cell comprises—a porousfirst electrode comprising at least one first lipophilic layer and atleast one second hydrophilic layer, wherein the first lipophilic layerand the second hydrophilic layer are porous, and—a second electrode; atleast one first supply device for the supply of a first solution ormixture of a first organic material which is soluble in or miscible witha first nonpolar solvent in or with a first nonpolar solvent, or for thesupply of a first organic material which is soluble in or miscible witha first nonpolar solvent, which is set up to supply the first solutionor mixture of the first organic material in or with the first nonpolarsolvent, or to supply the first organic material, to the electrolysiscell in such a way that the first organic solution or mixture or thefirst organic material makes contact with the first lipophilic layer ofthe first electrode; and at least one first removal device for theremoval of the remaining first solution or mixture and optionally atleast one first product of the electrochemical conversion of the firstorganic material (according to whether or not it is polar and canaccordingly be transferred to the first polar electrolyte), or of theremaining first organic material and optionally at least one firstproduct, or of the remaining first nonpolar solvent and optionally atleast one first product, or of at least one first product, which is setup to remove the remaining first solution or mixture and optionally atleast the first product of the electrochemical conversion of the firstorganic material, or the remaining first organic material and optionallyat least the first product, or the remaining first nonpolar solvent andoptionally at least the first product, or at least the first productfrom the electrolysis cell; further comprising at least one secondsupply device for a first polar electrolyte, which is set up to supplythe first polar electrolyte to the electrolysis cell in such a way thatthe first polar electrolyte makes contact with the second hydrophiliclayer of the first electrode and the second electrode, and/or a secondremoval device for the first polar electrolyte and optionally at leastone first product of the electrochemical conversion of the first organicmaterial, which is set up to remove the first polar electrolyte andoptionally at least one first product of the electrochemical conversionof the first organic material from the electrolysis cell.

The apparatus of the invention comprises at least one second supplydevice for the first polar electrolyte which is set up to supply thefirst polar electrolyte to the electrolysis cell in such a way that thefirst polar electrolyte makes contact with the second hydrophilic layerof the first electrode and the second electrode, if appropriate thefourth hydrophilic layer of the second electrode, and/or a secondremoval device for the first polar electrolyte and optionally at leastone first product of the electrochemical conversion of the first organicmaterial, which is set up to remove the first polar electrolyte andoptionally at least one first product of the electrochemical conversionof the first organic material from the electrolysis cell. These arelikewise not particularly restricted, provided that they are suitablefor the corresponding materials, and can also be executed in the form ofpipes, conduits, etc. However, if the first polar electrolyte is notconverted or does not undergo any overall change in the electrochemicalconversion in the electrolysis cell, and also no product from theelectrochemical conversion of the first organic material and optionallyof the first nonpolar solvent is transferred into it, it would also beconceivable that the second supply device and/or the second removaldevice is dispensed with, for example when no water is consumed in theelectrolysis in an aqueous first polar electrolyte. For heat-relatedreasons, however, even in such cases, the first polar electrolyte issupplied and removed, and so the corresponding supply and removal deviceis present.

If at least one first polar product (and/or second polar product giventhe appropriate configuration of the second electrode) is formed in theelectrochemical conversion and is transferred to the first (and/orsecond) polar electrolyte, extraction (optionally by means of one ormore separators) can also be effected into further polar electrolyteswithin the first electrolysis cell, such that, correspondingly, furthersupply and removal devices may also be provided for further polarelectrolytes.

The apparatus of the invention can especially be used to perform themethod of the invention. Correspondingly, the above details of themethod of the invention, especially those relating to constituents ofthe apparatus such as an electrolysis cell and components thereof, arealso applicable in the case of the apparatus of the invention, andreference is thus made here to this as well. Particularly theconfigurations of the first and second electrodes in the case of theapparatus of the invention correspond to those as discussed above forthe method of the invention. In addition, the electrolysis cell in theapparatus of the invention comprises at least one power source, and mayadditionally also comprise the constituents that have been mentioned forthe method of the invention, such as separators, pumps, valves, heatingand/or cooling devices, etc.

In particular embodiments, the first electrode and/or optionally thesecond electrode (especially when it comprises the third lipophiliclayer and the fourth hydrophilic layer) comprises a current collectorwhich is not in contact with the second hydrophilic layer or, ifappropriate, with the fourth hydrophilic layer. This type of electrodeis advantageous when the solubility of a substrate, i.e. of thecorresponding organic material, in aqueous electrolytes is too low toachieve suitable current densities or the separation of the product fromthe electrolytes is very costly.

The first and/or second electrode may also take the form of vapordiffusion electrodes/gas diffusion electrodes. In this electrolytedesign, the first and/or second organic material as substrate may beborne by a nonpolar phase that flows through, or through the reverseside of, the electrode. In principle, this phase may also be a substratevapor, a vapor carrier gas mixture or else a clean gaseous substrate. Inthis latter specific case, the amphiphilic electrode would become a gasdiffusion electrode. It is not impossible that the organic materialundergoes a phase transition during the electrochemical process. Aliquid substrate can also lead to a gaseous product. A gaseous substratemay also result in a product having a higher boiling point thatcondenses after the conversion.

In particular embodiments, the first lipophilic layer compriseshydrophobic, preferably conductive, first particles and/or at least onefirst hydrophobic binder.

In particular embodiments, the second hydrophilic layer comprises afirst electrocatalyst and optionally at least one second binder. Inparticular embodiments, the second hydrophilic layer comprises a firstion-conducting additive, especially a cation or anion exchanger, and/orfirst hydrophilic additives, especially metal oxides.

In particular embodiments, the second hydrophilic layer of the firstelectrode makes at least partial contact with a first separator. It hasalready been stated that the electrodes may contain a fused membrane.This membrane may also be utilized jointly by both electrodes inparticular embodiments. In this case, the membrane swollen with thefirst polar electrolyte, for example a water-swollen membrane, becomesthe polar, for example aqueous, phase, and a membrane-electrode assembly(MEA) may be formed. Especially in the case of non-water-releasingreactions, however, saturation of the organic phase with water maypossibly be required. The membrane is not limited in terms of its ionconductivity. The functionalization of the membrane polymers can bematched to the demands of the specific reaction. Therefore, thismembrane can be realized as a cation exchange membrane, anion exchangemembrane or bipolar membrane in either direction.

The first supply device and the first removal device are notparticularly restricted, provided that they are suitable for the supplyand removal of the corresponding material, and may take the form, forexample, of pipes, conduits, etc.

In particular embodiments, the second electrode comprises at least onethird lipophilic layer and at least one fourth hydrophilic layer,wherein the third lipophilic layer and the fourth hydrophilic layer arepreferably porous, wherein the second hydrophilic layer and the fourthhydrophilic layer are opposite one another but preferably not in contactwith one another in the electrolysis cell, further comprising at leastone further supply device for the supply of a second solution or mixtureof a second organic material which is soluble in or miscible with asecond nonpolar solvent in or with a second nonpolar solvent, or for thesupply of a second organic material which is soluble in or miscible witha second nonpolar solvent, which is set up to supply the second solutionor mixture of the second organic material in or with the second nonpolarsolvent, or the second organic material, to the electrolysis cell insuch a way that the second organic solution or mixture or the secondorganic material makes contact with the third lipophilic layer of thesecond electrode; and at least one further removal device for theremoval of the remaining second solution or mixture and optionally atleast one second product of the electrochemical conversion of the secondorganic material, or of the remaining second organic material andoptionally at least one second product, or of the remaining secondnonpolar solvent and optionally at least one second product, or of atleast one second product, which is set up to remove the remaining secondsolution or mixture and optionally at least the second product of theelectrochemical conversion of the second organic material, or theremaining second organic material and optionally at least the secondproduct, or the remaining second nonpolar solvent and optionally atleast the second product, or at least the second product from theelectrolysis cell.

If, in such embodiments, at least one first polar (organic) product isformed at the first electrode and at least one second polar (organic)product at the second electrode, it is not impossible that both aretransferred into the first polar electrolyte. Preference is given here,however, to providing a separator between the two electrodes, such thatthe at least one first polar product is transferred into the first polarelectrolyte and the at least one second polar product into a further(e.g. second) polar electrolyte that may be different than or correspondto the first polar electrolyte. When the at least one first polarproduct and the at least one second polar product are transferred intothe first polar electrolyte, however, it is not impossible that the twoare then allowed to react.

In these embodiments, the second hydrophilic layer and the fourthhydrophilic layer are opposite one another in the electrolysis cell, butpreferably do not make contact, especially when they are bothconductive. However, they may make partial contact if they arenonconductive provided that it can be ensured that the first electrodeand the second electrode come into contact with the first polarelectrolyte. However, this is not preferred.

The at least one further supply device for supply of a second solutionor mixture of a second organic material which is soluble in or misciblewith a second nonpolar solvent in or with a second nonpolar solvent, orfor the supply of a second organic material which is soluble in ormiscible with a second nonpolar solvent, and the at least one furtherremoval device for the removal of the remaining second solution ormixture and optionally at least one second product of theelectrochemical conversion of the second organic material, or of theremaining second organic material and optionally at least one secondproduct, or of the remaining second nonpolar solvent and optionally atleast one second product, or of at least one second product, are alsonot particularly restricted, provided that they are suitable for supplyand removal of the corresponding material, and may take the form, forexample, of pipes, conduits, etc.

In particular embodiments, the third lipophilic layer compriseshydrophobic, preferably conductive, third particles that may correspondto or be different than the first particles, and/or at least one secondhydrophobic binder that may correspond to or be different than thesecond hydrophobic binder.

In particular embodiments, the fourth hydrophilic layer comprises asecond electrocatalyst that may correspond to or be different than thefirst electrocatalyst, and optionally at least one fourth binder thatmay correspond to or be different than the second binder. In particularembodiments, the fourth hydrophilic layer comprises a secondion-conducting additive that may correspond to or be different than thefirst ion-conducting additive, especially a cation or anion exchanger,and/or second hydrophilic additives, especially metal oxides, that maycorrespond to or be different than the first hydrophilic additives.

In particular embodiments, the second hydrophilic layer of the firstelectrode and the fourth hydrophilic layer of the second electrode makeat least partial contact with a first separator on opposite sides of thefirst separator. In such embodiments, a first polar electrolyte is atleast partly present in the first separator. In particular embodiments,the first separator has been swollen by the first polar electrolyte.

In particular embodiments, the apparatus of the invention is anelectrolysis system. In particular embodiments, an electrolysis systemof the invention comprises a multitude of electrolysis cells that may beconstructed in accordance with the electrolysis cell detailed by way ofexample.

In particular embodiments, the apparatus of the invention furthercomprises at least one recycling device for the first nonpolar solventand/or the first organic material, the first polar electrolyte,optionally further polar electrolytes and/or optionally the second polarsolvent and/or the second organic material, optionally also comprisingcorresponding separation devices and/or purifying devices for provisionthereof.

In particular embodiments, the apparatus of the invention furthercomprises an external device for electrolyte treatment at least of thefirst polar electrolyte, optionally with a feed for lost electrolyte orconstituents thereof.

By the method of the invention and with the apparatus of the invention,it is possible to conduct a multitude of electrochemical conversions oforganic compounds, some of which are set out hereinafter by way ofexample.

Examples of cathodic transformations: Many organic conversions can beconducted electrochemically. These may include various hydrogenationreactions of polar and nonpolar multiple bonds. Reductive bond cleavagesare also possible.

Examples of anodic transformations: Oxidations of alcohols or oxidativecompounds are also possible. The Kolbe coupling of adipic monoesters togive dialkyl sebacates has been the subject of intense study in thepast, but has not been implementable owing to the high cell voltages asa result of the acetonitrile-based solvent. It is also possible tooxidatively couple alkynes.

The method of the invention is also of interest for pharmaceuticalsyntheses since the avoidance of catalysts present in solution orsuspension in the synthesis here means that these can correspondinglyalso be avoided in the product—for example in the case of heavy-metalcatalysts.

For the apparatus of the invention—as becomes clear from the abovevariations—various cell concepts are possible, some of which aredescribed by way of example hereinafter.

A first illustrative embodiment of an electrolysis cell with anamphiphilic electrode is shown in schematic form in FIG. 1.

A working electrode 1 here comprises a first lipophilic layer 2 which ispreferably hydrophobic and is in contact with a nonpolar phase 5, and asecond hydrophilic layer which is in contact with a first polarelectrolyte 6. The first polar electrolyte is additionally in contactwith the counterelectrode 4.

Further embodiments based on this embodiment are shown in FIGS. 2 to 4,these embodiments showing a basic mode of operation for theseamphiphilic electrodes in combination with a water-consumingcounterelectrode that evolves H₂ or O₂.

In FIG. 2, the nonpolar phase is routed here through the first cellspace I, forming a nonpolar product P from an organic material asreagent R, while the first polar electrolyte E is pumped through thesecond cell space II. A large part of the construction in FIG. 3corresponds to that in FIG. 2, except that the second electrode 4adjoins the first electrode 1, with insulation correspondingly presenthere between the two electrodes. The second electrode 4 here is porousin order that the first polar electrolyte E can make contact with thefirst electrode 1. In FIG. 4, the cell space II is divided into two cellspaces II, II⁺, as a result of which liquid flows around the secondelectrode 4. For protection of the first electrode 1, the secondelectrode 4 adjoins a separator S.

It is more sensible, however, to execute both electrodes in the cell bymeans of amphiphilic electrodes, as shown by way of example in FIG. 5and FIG. 6. In this case, both electrodes can be used forelectrochemical conversions of nonpolar reagents R1, R2 to nonpolarproducts P1, P2 in the amphiphilic cells as cathode K and anode A withadditional benefits, with the two electrodes in FIG. 6 divided by acommon separator S, here by way of example in the form of a commonmembrane containing polar electrolyte. The maximum Faraday efficiency inthat case is 200%. Since all electroorganic transformations are protontransfers, transformations in this cell type can be divided into threecategories. (Hereinafter: RED: reduction; OX: oxidation; REDOX: redoxreaction; R: organic radical; Et: ethyl)

Non-water-consuming or water-generating processes: in these processes,water is converted locally into OH⁻ or H⁺, but the water is regeneratedin the bulk electrolyte. These systems (theoretically) do not requireany electrolyte.

e.g.: aldehyde reduction+Kolbe coupling of adipic acidRED: R—CHO+2e⁻+2H₂O→R—CH₂—O +2OH⁻OX: 2EtO₂C—(CH₂)₄—CO₂H→EtO₂C—(CH₂)₈—CO₂Et+2e⁻+2H⁺+2CO₂Electrolyte: −2H₂O+2OH⁻+2H⁺=0REDOX: R—COH+2EtO₂C—(CH₂)₄—CO₂H→R—CH₂—OH+2CO₂+EtO₂C—(CH₂)₈—CO₂Et

Water-consuming processes: in these processes, water is consumedoverall. The electrolyte therefore has to be supplemented continuouslywith water.

e.g.: aldehyde reduction+alcohol oxidationRED: R—CHO+2e⁻+2H₂O→R—CH₂—OH+2OH⁻I×2OX: R—CH₂—OH+H₂O→R—COOH+4e⁻+4H⁺Electrolyte: −2H₂O+2OH⁻—H₂O+2H⁺=−H2OREDOX: 2R—COH+R—CH₂—OH+H₂O→2R—CH₂—OH+R—COOH

Water-generating processes: in these processes, water is releasedoverall. The electrolyte thus has to be continuously concentrated.

e.g.: nitro reduction+oxidative alkyne couplingRED: R—NO₂+6e⁻+4H₂O→R—NH₂+6OH⁻OX: 2R—CCH→R—CC—CC—R+2e⁻+2H⁺I×3Electrolyte: −4H₂O+6OH⁻+6H⁺=+2H₂OREDOX: R—NO₂+6R—CCH→R—NH₂+3R—CC—CC—R+2H₂O

Further possible applications of the method of the invention and also ofthe apparatus of the invention can be found, for example, in Fritz Beck,Berichte der Bunsen-Gesellschaft 1973,77 (10/11), 810-817; F. Beck, H.Guthke Chemie-Ing.-Technik. 1969, 41 (17), 943-950; DE1643693A1;DE2023080A1; DE2336288A1; DE2345461A1; and DE3615472A1.

The present invention is notable here for the use of specific electrodesfor performance of the electroorganic redox processes at a phaseboundary.

The above embodiments, configurations and developments can be combinedwith one another as desired if viable. Further possible configurations,developments and implementations of the invention also includecombinations, not specified explicitly, of features of the inventionthat have been described above or are described hereinafter in theworking examples. More particularly, the person skilled in the art willalso add individual aspects as improvements or supplementations to therespective basic form of the present invention.

The invention is elucidated further in detail hereinafter with referenceto various examples thereof. However, the invention is not limited tothese examples.

EXAMPLE 1

An illustrative cell construction was realized according to FIG. 1.

In this case, the electroreduction of nitrobenzene to aniline wasdemonstrated. The first polar electrolyte was realized by an aqueous 0.5M K₂SO₄ solution. The counterelectrode, an IrO₂-coated Ti sheet, assecond electrode consumed water in a 2.5 M KOH and was separated by aCEM, Nafion N11, in order to prevent reoxidation of the partlywater-soluble aniline product. The nonpolar organic phase was a 5 Msolution of nitrobenzene in diethyl ether (50 times the concentrationcompared to the maximum solubility in pure water). The phases werepumped along either side of the working electrode as first electrode.The latter consisted of a carbon GDL (Freudenberg H23 C2) as hydrophobiclayer (in contact with the nonpolar phase) and a dendritic coppercatalyst bound to an anion exchange resin as hydrophilic layer (incontact with the first polar electrolyte). The dendritic copper catalystbound to anion exchange resin was described in: “SelectiveElectroreduction of CO₂ toward Ethylene on Nano-Dendritic CopperCatalysts at High Current Density”; Christian Reller,* Ralf Krause,Elena Volkova, Bernhard Schmid, Sebastian Neubauer, Andreas Rucki,Manfred Schuster, and Gunter Schmid; Adv. Energy Mater. 2017, 1602114

FIG. 7 shows the working electrode potential E_(WE) versus asilver-silver chloride electrode in nitrobenzene bulk electrolysis.

The supply with organic phase was switched on 3 min after the current. Aspontaneous rise in the working electrode potential is observed, whichsuggests that the electrode has switched from hydrogen production tonitro reduction. The drop in gas evolution at the working electrode wasalso observed.

After 38 min, the organic phase was stopped, which led to irreversiblesaturation of the entire electrode in the aqueous phase. Afterswitch-on, it was no longer possible to continue the supply, which showsthat the substrate is indeed supplied directly from the organic phaseand not by extraction of the substrate into the aqueous phase.

1H NMR analysis of the aqueous and organic phase showed that the onlyproduct of this conversion was aniline. FIG. 8 shows the NMR spectrum ofthe organic phase after the electrolysis. No products are observed apartfrom aniline.

1. A method of electrochemical conversion of a first organic materialwhich is soluble in or miscible with a first nonpolar solvent, themethod comprising: introducing the first organic material into the firstnonpolar solvent to produce a first organic solvent or mixture;providing an electrolysis cell comprising a porous first electrodecomprising at least one first lipophilic layer and at least one secondhydrophilic layer, where the first lipophilic layer and the secondhydrophilic layer are porous, and a second electrode; introducing thefirst organic solution or mixture into the electrolysis cell in such away that the first organic solution or mixture makes contact with thefirst lipophilic layer of the first electrode; introducing a first polarelectrolyte into the electrolysis cell in such a way that the firstpolar electrolyte makes contact with the second hydrophilic layer of thefirst electrode and the second electrode; and electrochemicallyconverting the first organic material at the first electrode; orproviding an electrolysis cell comprising a porous first electrodecomprising at least one first lipophilic layer and at least one secondhydrophilic layer, where the first lipophilic layer and the secondhydrophilic layer are porous, and a second electrode; introducing thefirst organic material in the form of a liquid or gas into theelectrolysis cell in such a way that the first organic material makescontact with the first lipophilic layer of the first electrode;introducing a first polar electrolyte into the electrolysis cell in sucha way that the first polar electrolyte makes contact with the secondhydrophilic layer of the first electrode and the second electrode; andelectrochemically converting the first organic material at the firstelectrode; wherein the first nonpolar solvent and the first polarelectrolyte or the first organic material in the form of a liquid or gasand the first polar electrolyte form a first phase boundary with oneanother in such a form that the first phase boundary in theelectrochemical conversion is at least partly within the firstelectrode, preferably at an interface between the first lipophilic layerand the second hydrophilic layer.
 2. The method as claimed in claim 1,wherein the first polar electrolyte is liquid.
 3. The method as claimedin claim 1, wherein the first electrode comprises a first currentcollector which is not in contact with the second hydrophilic layer. 4.The method as claimed in claim 1, wherein the first lipophilic layer haszero catalytic activity in respect of the first polar electrolyte,and/or wherein the first lipophilic layer comprises hydrophobic firstparticles and/or at least one first hydrophobic binder.
 5. The method asclaimed in claim 1, wherein the second hydrophilic layer comprises afirst electrocatalyst and optionally at least one second binder, and/orwherein the second hydrophilic layer comprises a first ion-conductingadditive, and/or first hydrophilic additives.
 6. The method as claimedin claim 1, wherein the second hydrophilic layer of the first electrodemakes at least partial contact with a first separator.
 7. The method asclaimed in claim 1, wherein the second electrode comprises at least onethird lipophilic layer and at least one fourth hydrophilic layer,wherein the third lipophilic layer and the fourth hydrophilic layer arepreferably porous, wherein the first polar electrolyte makes contactwith the fourth hydrophilic layer of the second electrode, furthercomprising introducing—a second organic material in the form of a liquidor gas, or—a second organic solution or mixture comprising a secondorganic material which is soluble in or miscible with a second nonpolarsolvent, and a second nonpolar solvent, into the electrolysis cell insuch a way that the first organic material or the second organicsolution or mixture makes contact with the third lipophilic layer of thesecond electrode, wherein the second organic material iselectrochemically converted at the second electrode.
 8. The method asclaimed in claim 7, wherein the second hydrophilic layer of the firstelectrode and the fourth hydrophilic layer of the second electrode makeat least partial contact with a first separator on opposite sides of thefirst separator, wherein the first polar electrolyte is at least partlypresent in the first separator.
 9. An apparatus for electrochemicalconversion of a first organic material which is soluble in or misciblewith a first nonpolar solvent, comprising: an electrolysis cell, whereinthe electrolysis cell comprises a porous first electrode comprising atleast one first lipophilic layer and at least one second hydrophiliclayer, wherein the first lipophilic layer and the second hydrophiliclayer are porous, and a second electrode; at least one first supplydevice for the supply of a first solution or mixture of a first organicmaterial which is soluble in or miscible with a first nonpolar solventin or with a first nonpolar solvent, or for the supply of a firstorganic material which is soluble in or miscible with a first nonpolarsolvent, which is set up to supply the first solution or mixture of thefirst organic material in or with the first nonpolar solvent, or tosupply the first organic material, to the electrolysis cell in such away that the first organic solution or mixture or the first organicmaterial makes contact with the first lipophilic layer of the firstelectrode; and at least one first removal device for the removal of theremaining first solution or mixture and optionally at least one firstproduct of the electrochemical conversion of the first organic material,or of the remaining first organic material and optionally at least onefirst product, or of the remaining first nonpolar solvent and optionallyat least one first product, or of at least one first product, which isset up to remove the remaining first solution or mixture and optionallyat least the first product of the electrochemical conversion of thefirst organic material, or the remaining first organic material andoptionally at least the first product, or the remaining first nonpolarsolvent and optionally at least the first product, or at least the firstproduct from the electrolysis cell; and at least one second supplydevice for a first polar electrolyte, which is set up to supply thefirst polar electrolyte to the electrolysis cell in such a way that thefirst polar electrolyte makes contact with the second hydrophilic layerof the first electrode and the second electrode, and/or a second removaldevice for the first polar electrolyte and optionally at least one firstproduct of the electrochemical conversion of the first organic material,which is set up to remove the first polar electrolyte and optionally atleast one first product of the electrochemical conversion of the firstorganic material from the electrolysis cell.
 10. The apparatus asclaimed in claim 9, wherein the first electrode comprises a firstcurrent collector that is not in contact with the second hydrophiliclayer.
 11. The apparatus as claimed in claim 9, wherein the firstlipophilic layer comprises hydrophobic first particles and/or at leastone first hydrophobic binder.
 12. The apparatus as claimed in claim 9,wherein the second hydrophilic layer comprises a first electrocatalystand optionally at least one second binder, and/or wherein the secondhydrophilic layer comprises a first ion-conducting additive, and/orfirst hydrophilic additives.
 13. The apparatus as claimed in claim 9,wherein the second hydrophilic layer of the first electrode makes atleast partial contact with a first separator.
 14. The apparatus asclaimed in claim 9, wherein the second electrode comprises at least onethird lipophilic layer and at least one fourth hydrophilic layer,wherein the third lipophilic layer and the fourth hydrophilic layer areporous, wherein the second hydrophilic layer and the fourth hydrophiliclayer are opposite one another but not in contact with one another inthe electrolysis cell, further comprising: at least one further supplydevice for the supply of a second solution or mixture of a secondorganic material which is soluble in or miscible with a second nonpolarsolvent in or with a second nonpolar solvent, or for the supply of asecond organic material which is soluble in or miscible with a secondnonpolar solvent, which is set up to supply the second solution ormixture of the second organic material in or with the second nonpolarsolvent, or the second organic material, to the electrolysis cell insuch a way that the second organic solution or mixture or the secondorganic material makes contact with the third lipophilic layer of thesecond electrode; and at least one further removal device for theremoval of the remaining second solution or mixture and optionally atleast one second product of the electrochemical conversion of the secondorganic material, or of the remaining second organic material andoptionally at least one second product, or of the remaining secondnonpolar solvent and optionally at least one second product, or of atleast one second product, which is set up to remove the remaining secondsolution or mixture and optionally at least the second product of theelectrochemical conversion of the second organic material, or theremaining second organic material and optionally at least the secondproduct, or the remaining second nonpolar solvent and optionally atleast the second product, or at least the second product from theelectrolysis cell.
 15. The apparatus as claimed in claim 14, wherein thesecond hydrophilic layer of the first electrode and the fourthhydrophilic layer of the second electrode make at least partial contactwith a first separator on opposite sides of the first separator, whereina first polar electrolyte is at least partly present in the firstseparator.
 16. The method as claimed in claim 2, wherein the first polarelectrolyte contains water and optionally at least one salt.
 17. Themethod as claimed in claim 4, wherein the first lipophilic layercomprises hydrophobic, conductive, first particles.
 18. The method asclaimed in claim 5, wherein the second hydrophilic layer comprises afirst ion-conducting additive comprising a cation or anion exchanger,and/or first hydrophilic additives comprising metal oxides.
 19. Themethod as claimed in claim 8, wherein the first separator has beenswollen by the first polar electrolyte.
 20. The apparatus as claimed inclaim 11, wherein the first lipophilic layer comprises hydrophobic,conductive, first particles.
 21. The apparatus as claimed in claim 12,wherein the second hydrophilic layer comprises a first ion-conductingadditive comprising a cation or anion exchanger, and/or firsthydrophilic additives comprising metal oxides.
 22. The apparatus asclaimed in claim 15, wherein the first separator has been swollen by thefirst polar electrolyte.